1. Field of the Invention
The present invention relates to the field of liquid crystal display technology, and in particular to a black matrix mask, a method for manufacturing a black matrix, and an application thereof.
2. The Related Arts
Recently, low temperature poly-silicon (LTPS) panels have gained wide applications in high-end mobile phones and tablet computers. The LTPS panels use low temperature poly-silicon that has high mobility to make a thin-film transistor. Such panels have advantages, including high resolution, low power consumption, high response speed, and high aperture ratio and will potentially become the next generation for medium- and small-sized display panels.
Due to the trend for pursuit of higher PPI (pixels per inch) for LTPS products, the line width of a black matrix (BM) of a color filter is getting smaller and smaller. With the narrowing of the line width of the black matrix, an angle of a taper of the black matrix needs to be made more approaching to 90 degrees in order to prevent reduction of aperture ratio due to increase of PPI. However, the known black matrix materials are constrained from having a taper angle thereof exceeding 90 degrees due to the need for better processability Referring to FIG. 1A, a schematic view is given to illustrate a taper angle of a conventional black matrix. As a part of a complete liquid crystal panel or a color filter structure, the black matrix 11 is formed on a first base plate 10 and is arranged between the first base plate 10 and a second base plate 20. Light emitting from a backlight source transmits through the second base plate 20 and travels toward the first base plate 10. The black matrix 11 has a line width of 5 micrometers and a taper angle A less than 90 degrees. The smaller the taper angle A of the black matrix 11 is, the more easily light will be shielded, the smaller the aperture ratio will be, and the lower the transmission rate will be. Referring to FIG. 1B, a schematic view is given to illustrate an ideal taper angle of a black matrix. Under the same condition of light width being 5 micrometers, ideally, the black matrix 12 located between the first base plate 10 and the second base plate 20 has a taper angle A that can be made greater than 90 degrees, such that the larger the angle is, the larger the aperture ratio will be and the higher the transmission rate will be.
Referring to FIGS. 2A-2D, FIG. 2A is a schematic view illustrating a conventional black matrix manufacturing process; FIG. 2B is a mask pattern used in the conventional black matrix manufacturing process; FIG. 2C is a mask used in the conventional black matrix manufacturing process; and FIG. 2D is a conventional black matrix manufactured. The conventional black matrix manufacturing process generally comprises exposure, development, and baking. During such a process, the black matrix material layer 30 undergoes continuous deformation to finally form a black matrix 31 on a base plate 32. Firstly, the mask 33 shown in FIG. 2C is used to subject a black matrix material layer 30 to exposure, where the mask 33 comprises a mask pattern 34 provided thereon. Under this condition, crosslink is induced on a surface of the black matrix material layer 30. Next, the exposed black matrix material layer 30 is subjected to development, in which a development solution corrodes into a bottom layer of the black matrix material layer 30 to form an undercut, so that eaves of the taper is relatively long. Thus, during a subsequent operation that the black matrix material layer 30 is subjected to post baking, the black matrix material layer 30 will easily undergo thermal flow, moving in the direction indicated by arrows to make the taper smooth so as to finally forming the black matrix 31 on the base plate 32. Such a black matrix 31 manufactured with the known process involves the drawback of being hard to get the taper exceeding 90 degrees, making it adverse to increase of aperture ratio.